Discharge tube voltage transformers



Dec. 20, 1955 J. H. COLEMAN 2,727,987

DISCHARGE TUBE VOLTAGE TRANSFORMERS Filed March 18, 1950 2 sh t s t 1 BY Z X ATTORNEY w 6 i D 7 7 WM w 0 7 r mm m l e w "m: 0 n 1 w w 1 w raw--- .11 Hr Z J 5.! IL 9 m l H .C F Q a mi HM by a! a T1 W FEET M 5. a J WM -Vw Z M w E r m 5 7 w 7 I WW y. f 7 i F H 4. M41! h Z4. 7/. /W 5% H 32 N F 2% m N 4 0 v 7 1955 J. H. COLEMAN DISCHARGE TUBE VOLTAGE TRANSFORMERS 2 Sheets-Sheet 2 Filed March 18, 1950 a o o 0 o N [m HUAM H INVENTOR can I .failrzJiQlalm a 7 w M/Pflf ATTORNEY 2,727,987 DISCHARGE TUBE VOLTAGE TRANSFORMERS John H. Coleman, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application March 18, 1950, Serial No. 150,530 18 Claims. (Cl. 250-27) This application is a continuation-in-part of applicants copending United States application Serial No. 67,796 filed December 28, 1948, now abandoned.

This invention relates generally to discharge tube voltage transformers and particularly to such transformers using increased or decreased energy electrons for providing unidirectional output voltages in response to applied unidirectional or alternating potentials.

The principal object of the invention is to provide a new method of and apparatus for the transformation of an applied unidirectional or alternating voltage to another unidirectional voltage.

Another object of the invention is to provide such a voltage transformer in which electrons are caused to interact with each other-within a confined or trapping space, whereby the energy of some electrons is changed, and some of said changed energy electrons are collected and utilized. 1

A further object of the invention is to provide such a voltage transformer in which use is made of the excess energy electrons present in a magnetron-like structure.

Another object of the invention is to provide such a voltage transformer in which use is made of electrons which have lost energy in a device of the type described.

A further object is to provide novel methods of and means for rectifying and dividing alternating potentials.

Other objects will be apparent from the disclosure of the invention as hereinafter set forth in detail and from the drawings made part hereof. In the drawings:

Figure l is a partially schematic cross-sectional view of an embodiment of the invention in which the interaction or trapping space is defined by an axially positioned cathode and a surrounding anode and the anode is surrounded by a collector;

Figure 2 is a graph showing the relation between the anode current and the magnetic field in the device for a constant value of anode voltage;

Figure 3 is a graph showing the relation between values of the collected currents and the potential of the collector in the device for a constant value of magnetic field;

Figure 4 is a partially schematic cross-sectional view of a modification of the structure shown in Figure 1, wherein a collector is positioned in the axis of a device and the cathode surrounds a grid-form anode and the collector;

Figure 5 is a partially schematic cross-sectional view of another modification of the structure of Figure 1 in which the collector is connected to the cathode through a load resistance and the cathode surrounds the anode with end plates extending radially inward from the cathode;

Figure 6 is a partially schematic cross-sectional view of a combination of the devices of Figures 4 and 5, with provisions for impressing an inhomogeneous magnetic field upon the medium within the envelope of the device;

Figure 7 is a graph illustrative of the relations between other operating parameters according to the invention; and

States Patent C) be negative relative to the cathode 2,727,937 Patented Dec. 20, 1955 Figure 8 is a cross-sectional, partially schematic view of a rectifier embodiment of the invention.

Similar reference characters are applied to similar elements throughout the drawings.

Referring to Figure l, a device according to the invention includes a magnetic permeable evacuated envelope 1. In the axis of envelope 1 is mounted a hot thermionic or cold cathode 2 to which are attached end plates 3, to confine the electrons emitted from cathode 2 within the central portion of the envelope 1. Surrounding and coaxial with cathode 2 is an anode 4, which is in the form of a grid or apertured electrode. The cathode 2 and surrounding anode 4 define an electron interaction or trapping space therebetween which is not obstructed by the presence of any other electrodes. Concentric with and outside anode 4 is a hollow cylindrical collector electrode 5. An output load resistance 6 is connected between collector 5 and cathode 2 through ground 7. The anode power supply is furnished by electric source (V9,)8, which is connected between cathode 2 and anode 4. A constant magnetic field, indicated by the arrow H, is impressed on the medium axially the envelope 1 by any conventional means, such as by electromagnets, the poles of which are indicated at 9, Figure 5.

In operation, the magnetic field H is adjusted to a value just above cut-off point, that is, the magnetic field is brought to such a value that the electrons from cathode 2 are cut-off from striking the anode 4 and are returned toward the cathode 2. The relation between the cut-off magnetic field He, indicated in Fig. 2, and the anode potential Va (neglecting the initial velocity of the electrons) is given by the equation lai HF- e R where He is the strength of the field, m is the mass of the electron, e is the charge of the electron, Va, is the potential of the anode and R is the radius of the anode in cms.

As the electrons move away from and return to the cathode, and collisions occur in this reaction or trapping space and as a result of these collisions, some of the orbital energy of the electrons is converted into energy of random motion. This results in the formation of a region about the cathode in which the electron current is limited by space charge and the boundary of this region acts as a virtual cathode. Some of the electrons, because of their increased energy of random motion move toward and strike anode 4 and some anode current flows even when the magnetic field is increased beyond its cut-oif value. The graph in Figure 2 verifies this fact, where some anode current Ia was found to exist when the magnetic field was increased beyond the cut-01f value Ho.

Likewise, some of these excess energy electrons pass through anode 4 and are collected by collector 5. The potential of collector 5 is in proportion to the energy value of the electrons impinging thereon. It will be understood that the potential of the floating collector 5 will always 2, due to the charge received from the electrons collected.

The collector resistance characteristics have been plotted in Figure 3, where In is the collector current and Ve is the collector voltage, the values of the anode voltage Va and the magnetic field H being kept constant. The values of In versus Vc are plotted for values of V0 from +Ve to -Va. Since the collector 5 in Fig. 1 can never be positive relative to the cathode, operation of the device as a transformer is limited to that portion of the characteristic shown in Fig. 3 to the left of the vertical axis representing zero voltage. The region between zero voltage and Va is a voltage step-down region, since the output voltage across the load 6 is less than the input voltage Va. The region to the left of Va, that is, for negative values of Va greater than the positive anode voltage Va, is a voltage step-up region. The voltage drop across the load resistance 6 in Fig. 1 corresponds to the applied voltage Va in Fig. 3. The desired voltage ratio is obtained 'by choosing a load resistance R1 equal to the desired ratio Vc/Io as determined from the collector resistance characteristic (such as that of Fig. 3) for the particular tube involved. Thus it is seen that the collector can be operated over a wide range of negative voltages determined by the load resistance However, to obtain a voltage step-up the collector potential must be negative with respect to Va and the corresponding load resistance R1 must be greater than 1 where I is the collector current for --Va potential.

A modification of the structure shown in Figure 1 is shown in Figure 4. In this inverted magnetron-like structure, a collector of small cross-section is positioned in the axis of the envelope 1 and is surrounded by a grid-form anode 4, which in turn is surrounded by a hollow cylindrical cathode 2. End plates 3 extend radially inward from cathode 2.

The theoretical cut-off value of the magnetic field, He, is given by the equation 1 8m 277L811 WR V T CR0 (2) where Va. is the potential difierence between the anode and the cathode, R0 is the radius of the outer cylinder, b is the ratio of the outer and inner cylindrical radii, So is the tangential initial velocity of the electron, m is the mass of the electron, and e is the charge of the electron.

Comparing this arrangement with that of Figure 1, the collector 5 presents a smaller target, because of its size, but the trapping conditions are more favorable and the electrons attain higher excess energies. The results are that the potentials of collector 5 are higher than those attained by the arrangement of Figure l. The collector resistance characteristics of this latter arrangement are similar to those shown in Figure 3 but extend to higher negative voltages.

A second modification of the arrangements of Figure l is shown in Figure 5. In this arrangement, an anode 4 of small cross-section is positioned in the axis of the envelope 1, and the collector 5 is in the form of a hollow cylinder and presents a larger target than the collector in Fig. 4. The cathode 2 is formed of a series of rings 2a, connected together by bonding wire 10. This structure permits the excess energy electrons to pass through cathode 2 and fall upon collector Some of the excess energy electrons will strike cathode 2 and will be lost. This loss cannot be avoided, just as loss of some of the excess energy electrons cannot be avoided in the arrangements in Figures 1 and 4 when these electrons strike anode 4.

In Figure 6 is shown a combination of the arrangements disclosed in Figures 4 and 5. Collector 5a of small crosssection is positioned in the axis of the envelope 1, as in Figure 4, and collector 5b, cylindrical in shape, is positioned outside the cathode 2., which is similar to the cathode in Fig. 5. Anode 4 surrounds collector 5a and is positioned between cathode 2 and collector 5a.

In this arrangement collectors 5a and 5b are shown as being connected to load 6. Separate loads may be connected individually to collectors 5a and 5b, respectively, if desired.

There is also disclosed in Figure 6 an arrangement of magnets to impress upon the medium within the envelope an inhomogeneous magnetic field. The magnetic field between pairs of poles may be produced by permanent magnets or by conventional electromagnets. By the selection of coaxial magnets 11 and 12 of suitable strengths and relative positions, a relatively strong magnetic field may be impressed upon the medium in the vicinity of the two collectors 5a and 5b, with relative weaker fields in the trapping space between anode 4 and cathode 2.

The same structures as shown in Figs. 1, 4, 5 and 6 can be used to obtain a cold cathode glow discharge, by electron trapping to charge up the collector electrode, by inserting in the envelope 1 an ionizable gas between the pressure range of 10- to 10 mm. Hg. However, only a step-down in voltage can be obtained due to the presence of particles both positive and negative in almost equal numbers. Employing such a gas tube utilizing, for example, the structure of Figure 1, the measured collector resistance characteristics are shown in Figure 7. Here the electron current Ie is similar to the graph of Fig. 3. The positive ion current is indicated as L; and the resulting total current is indicated as It equal to the sum of (Io-l-Ip). Thus the only voltage region in which the collector can be operated is between the voltage V'ro at which IT is zero and zero voltage as a step-down transformer. As the load resistance R1 approaches zero the collector potential approaches zero,

Finally, as shown in Figure 8, employing a cold cathode, analternating voltage is applied between the cathode 2 and anode 4, in place of the D. C. voltage 8. Electron trapping occurs in the space between the cathode and the anode when the voltage on the anode 4 swings positive with respect to the cathode and no trapping occurs when the anode voltage is negative. These effects are described in greater detail in applicants copending United States application Serial No. 93,324 filed May 14, 1949, now Patent No. 2,615,139, dated October 21, 1952. Thus, the collector is charged positive on the positive half cycle of the anode to a value determined by the resistance of the load 6 and as shown in Figure 7.

Thus the two D. C. voltage outputs can be obtained across the loads R1 and R2. The tube and collector act as a rectifier with an internal voltage divider.

There is thus disclosed a device having one or more electrodes permeable to excess energy electrons and collectors upon which these electrons may fall, the electrons being trapped, some of which become excess energy electrons through the conversion of some of their orbital energy into energy of random motion, the medium in which the trapping and collection occurs being subject to a uniform or to an inhomogeneous magnetic field.

What is claimed is:

1. Apparatus for transforming an applied input voltage into a unidirectional voltage comprising an envelope containing a cathode electrode and an anode electrode spaced from each other and defining an unobstructed interaction space therebetween, at least one of said electrodes being electron permeable, and a collector adjacent said one electrode and outside said space, means for applying an input voltage between said electrodes, and means for establishing a constant magnetic field in said space in a direction transverse to the normal path of electrons between said electrodes, the strength of said field in said space being just above the cut-off value at the maximum amplitude of said input voltage in the polarity in which said anode electrode is positive relative to said cathode electrode, whereby said space is an electron trapping space wherein, as a result of collisions producing random electron motions, some of the electrons pass through said electronpermeable electrode to said collector.

2. Apparatus as in claim 1, wherein said collector is located adjacent said anode electrode.

3. Apparatus as in claim 1, wherein said collector is located adjacent said cathode electrode.

4. Apparatus as in claim 1, wherein said electrodes and.

said collector are coaxial and said magnetic field extends parallel to the axis thereof.

1 collector coaxially surrounding said first 5. Apparatus as in claim 4, wherein said cathode electrode surrounds said anode electrode.

6. Apparatus as in claim 4, wherein said anode electrode surrounds said cathode electrode.

7. Apparatus as in claim 4, further including end plates one at each end of said space and connected to said cathode to aid in trapping electrons in said space.

8. Apparatus as in claim 1, further including a load connected directly between said collector and said cathode electrode.

9. Apparatus as in claim 8, further including a second load connected in series with said means for applying an input voltage between said anode and cathode electrodes.

10. Apparatus as in claim 1, wherein both of said electrodes are electron permeable, and including a second collector adjacent the other of said electrodes and outside said interaction space.

11. Apparatus as in claim 10, wherein said electrodes and said collectors are coaxial and said magnetic field extends parallel to the axis thereo 12. Apparatus as in claim 1, wherein said envelope contains an ionizable medium at a pressure not substantially exceeding mm. of mercury.

13. An electron tube comprising an elongated non: emissive first collector, a cylindrical non-emissive second collector, elec tron permeable cathode and anode electrodes coaxially mounted intermediate said collectors, and means for establishing an axial magnetic field in the space between said electrodes.

14. An electron tube as in claim 13, wherein said collectors and said electrodes are mounted within an envelope containing an ionizable medium at a pressure not substantially exceeding 10- mm. of mercury.

15. An electron tube comprising a non-emissive anode, a cylindrical non-emisssive collector coaxially surrounding said anode, an electron permeable cathode coaxially mounted intermediate said anode and said collector, and

means for establishing an axial magnetic field in the space between said cathode and said anode.

16. An electron tube comprising a non-emissive collector, a cathode coaxially surrounding said collector, an electron permeable non-emissive anode coaxially mounted intermediate said collector and said cathode, and means for establishing an axial magnetic field in the space between said cathode and said anode.

17. An electron tube comprising an anode, a cylindrical output electrode coaxially surrounding said anode, an electron permeable cathode coaxially mounted inter mediate said anode and said output electrode, means for establishing an axial magnetic field in the space between said cathode and anode, and an output load connected directly between said output electrode and said cathode.

18. An electron tube comprising an output electrode, a cathode coaxially surrounding said output electrode, an electron permeable anode coaxially mounted intermediate said output electrode and said cathode, means for establishing an axial magnetic field in the space between said cathode and said anode, and an output load connected directly between said output electrode and said cathode.

References Cited in the file of this patent Linder Apr. 10, 1951 

